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Researchers report cost-effective synthesis of NiFe-layered double hydroxides nanosheets as efficient OER catalyst

A team from Brown University and Lakehead University (Canada) have developed a method for the facile and cost-effective synthesis of NiFe-layered double hydroxides (LDH) nanosheets to serve as efficient catalyst for the oxygen evolution reaction in an alkaline environment.

Compared to previously reported LDH catalysts, the new nanosheets exhibit a much higher oxygen evolution activity. The overpotential of catalytic OER was very low and the Tafel slope (Tafel analysis is a tool for comparing electrocatalytic activity and elucidating the reaction mechanism) was close to that of a commercial RuO2 catalyst. A paper describing their work is published in the journal Electrochemistry Communications.

Electrochemical water splitting offers one of the most attractive approaches in the realization of efficient energy conversion and storage. In Oxygen evolution reaction (OER), the overall efficiency of the complicated OER is severely influenced by the energy loss and large overpotential. To date, OER catalysts based on precious metal oxides RuO2 or IrO2 are most effective, but the high price and scarcity make them impractical to use on a large scale. Besides, it has been reported that the RuO2 and IrO2 catalysts display poor stability in alkaline solution. Toward this end, it is crucial to develop highly active and cost-effective OER catalysts based on earth-abundant metals.

… Recently, the low-cost NiFe-derived layered material, spinel and oxides were reported to display promising performances of OER in alkaline solutions. … However, LDHs still suffers from poor electronic conductivity and electron transportation. To reduce these drawbacks, the conductivity and activity of LDHs has been further enhanced by coupling to a carbon nanotube, graphene-like network or by exfoliation. … The resulted LDHs by exfoliation methods often display thin nanosheets with better conductivity and large space between the layers. However, the synthesis still requires multiple steps of LDH precursor synthesis, anion-exchange, exfoliation in high boiling point solvents (e.g., formamide or N-methylpyrrolidone) and final removal of these high boiling points solvent. The removal of high boiling point solvents often associates with the utilization of excessive ester and low yield of LDHs. Besides, the resulted LDHs plates often tend to stack and lack good control over the hierarchical nanostructures.

Herein, we have developed a facile, and cost-effective route to synthesize ultra-thin NiFe-LDHs nanosheets in the mixed solvent of ethanol and isopropanol.

—Yan et al.

The fabricated thin nanosheets display more active sites and improve electronic conductivity.

The new process comprised two steps:

  • LDH precursor was synthesized by a co-precipitation method at room temperature

  • Delamination was then performed, with LDHs dispersed into a mixed solvent of ethanol and isopropanol. The resulting suspension was centrifuged at 5000 rpm for 5 min and dried at 80 ˚C under vacuum conditions.

Resources

  • Kai Yan, Todd Lafleur, Jiajue Chai, Cody Jarvis (2016) “Facile synthesis of thin NiFe-layered double hydroxides nanosheets efficient for oxygen evolution,” Electrochemistry Communications, Volume 62, Pages 24-28, doi: 10.1016/j.elecom.2015.11.004

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